Underwater screening



May '12, 1953 E. o. SCHNEIDER UNDERWATER SCREENING FiledSept. 21. 1949 XNVENTOR box vi ATTORNEY I Patented May 12, 1953 UNDERWATER SCREENING Earl 0. Schneider, West Allis, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application September 21, 1949, Serial No. 116,891

8 Claims.

This invention relates to vibratory screening devices for separating solid particles of various sizes in a liquid medium such as water.

It has been previously known that heavy solids could be advantageously separated by screening on a vibratory screen at or below the surface of a body of liquid, with suitable arrangements for removal of separate products from the liquid bath. However, probably owing to the forces on the particles due to the movement of the liquid medium through the screen meshes, blinding by lodgment of the near mesh-size particles in the screen openings has made such screening largely impractical, the resulting reduction of effective screen area making necessary frequent stoppages for cleaning or screen cloth replacement.

By the present invention the objectionable blinding of underwater screens is avoided through combining with the screen and frame, cleaner retaining compartments under the cloth, and buoyant cleaner bodies in the compartments, which bodies are forced against the under surface of the screen by the buoyant eifect of the liquid medium, and moved by the screen movement in such a manner as to effect removal of most blinding particles before they have become too firmly lodged to permit dislodgment.

An object of the invention is t improve the effectiveness and eiliclency of underwater screening by continuously effecting dislodgment of blinding particles.

The invention having the above and still other objects and advantages is fully described hereinbelow with reference to the drawing in which the single figure represents a vertical longitudinal cross sectional view of a liquid-submerged vibratory screening device embodying the invention.

In the embodiment shown in the drawing, a tank I, of generally rectangular form, is provided with a divider ridge 2 and suitable product discharge openings: 3 for the through, or less thanmesh-size particles; and l for the over," or larger than mesh-size product. Conventional product removal devices (not shown) are attached to discharge openings 3 and 4, respectively, to provide for removal of solids while preventing free discharge of liquid mediumfrom the tank. A vibratory screen frame 6 withrconventional mechanism 1 for vibrating or reciproeating the frame, preferably in a vertical plane, is suspended within the tank I, as by spring supported cables 8 at the four corners, or other suitable known resilient supporting arrangement.

In the frame 6 a screen 9 is mounted, the

screen being of woven wire cloth, perforated plate, or any other known foraminous material through which solids may be sifted. In the form shown, the screen 9 is of wire cloth, provided with hooked ends, and is stretched lengthwise'of the frame as by conventional screen tensioning arrangements at opposite ends, indicated at H) and I I.

Below the screen 9, the space within frame 6 is divided by a number of transverse walls 12, into a plurality of rectangular compartments. Within each of these compartments a quantity of balls or cleaner bodies I3 areplaced, the balls; or other solid shapes, being of such material or construction as to be considerably lighter than an equivalent volume of the liquid medium in which they are submerged. It has been found that the ordinary table tennis ball (a hollow sphere of pyroxylin compound) makes an effective cleaner. However, any ball, cylinder, or irregular shape, of light material or construction, with a fairly hard, abrasion-resistant surface, may be used.

The compartments may be closed on the bottom by a coarsely meshed or perforated ball retainer I 4 to retain the cleaner bodies in their proper locations, as, for example, when the tank is emptied, or the screen frame removed from the tank.

In operation, the tank I is kept filled to a level above the screen 9 with a suitable liquid me dium; solid particles to be separated are fed to the screen surface, as by a chute l5; and the screen frame 6 is vibrated or reciprocated in a known manner to cause movement of the oversize particles along the screen 9 to the discharge end l6. Makeup water is supplied to tank I as by a spray system H. The buoyancy effect of the liquid medium causes the floating cleaner bodies to press against the under side of the screen clothing 9; and the motion of the screen relative to the liquid medium causes th cleaner bodies to move relative to the screen and tap against it in a manner to cause effective dise lodgment of any near mesh-size particles which may be lodged, or may tend to become lodged in the screen openings.

It will be understood that the device illustrated and described is illustrative of but one embodiment, and that the invention may readily be applied to screens of different construction The invention is therefore not limited to the specific structural features of the illustration, and includes such modifications and equivalent constructions as may readily occur to persons skilled in the art to which it appertains, within the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In apparatus for sizing material particles under water, the combination comprising: a tank for holding a body of water; a screen frame mounted for movement relative to. said tank and supporting a generally horizontal foraminous screen below the normal water level of said tank; walls attached to said screen frame defining a compartment enclosed on all sides by said walls and closed at the top by said screen, a plurality of cleaner bodies loosely disposed, insald compartment each having a density less. than water and each being greater in size than the openings in said screen; and means for repeatedly moving said frame and screen relative to said tank so as to cause said bodies to vibrate with respect to the under surface of said screen.

2. Ina, device for sizing materials under water, the combination comprising: tank means for immuring a body of water; a generally horizontal foraminous screen positioned below the normal water level of said tank means; means for repeatedly moving said screen relative to said tank means; walls defining a. compartment enclosed on all sides by said walls and closed at the top by said screen; and a, plurality of cleaner bodies loosely disposed in said compartment each having a density less, than water and each being greater in size than the openings in said screen.

3. In apparatus for sizing materials under water:; a tank for holding a body of water; a screen frame mounted for movement relative to said tank, and having a foraminous screen connected therewith positioned below the normal water level of saidtank; means repeatedly moving Said frame and screen relative to said tank; means defining a compartment enclosed on all sides by said wall means and closed at th top by said screen; and a plurality of cleaner bodies loosely disposed in said compartment each having a den.- sity' less than water and, each being greater in size than the. openings of said screen.

4. In apparatus for sizing material particles in a liquid medium, the combination comprising: a tank adapted to receive a body of liquid medium and provided with means for removal of solid products from a body of liquid medium disposed in said tank, a screen frame mounted for movement relative to said tank, a generally horizontal foraminous screen mounted on said frame in a position below the predetermined liquid level of said tank, walls attached to said screen frame defining a compartment enclosed on all sides by said walls and closed at the top by said screen, a plurality of cleaner bodies loosely disposed 'in said compartment each having a density less than the liquid medium in which they are to be submerged and each being greater in size than the openings in said screen, means for repeatedly moving said frame and screen relative to said body of liquid medium so as to cause said bodies to vibrate with respect to the under surface of said screen, and means for depositing material particles on the upper surface of said screen for treatment.

5. In a device for sizing materials in a liquid medium, the combination comprising: container means for immuring a body of liquid medium, a

generally horizontal foraminous screen mounted in a position below the predetermined level of said liquid medium, means for repeatedly moving said screen relative to said container means, walls defining a compartment enclosed on all sides by said walls and closed at the top by said screen, and a plurality of cleaner bodies loosely disposed in said compartment each having a density less than the liquid medium in which they are to be submerged and each being greater in size than the openings in said screen so that in operation they will be held submerged by said screen and vibrate with respect to the under surface of said screen.

6. In apparatus, for sizin materials in a liquid medium: a tank for receivin a liquid medium, a screen frame mounted for movement relative to said tank, a foraminous screen connected to said tank in, a position below the predetermined liquid level of said tank, means for supplying material to be sized to said screen, means repeatedly moving said frame. and screen relative to said body of liquid in a manner to cause movement of oversize particles along the upper surface of said screen, wall means defining a compartment below said screen enclosed on all sides by said wall means and closed at the top by said screen, and a plurality of cleaner bodies loosely disposed in said compartment each having a density less than the liquid medium in which they are to be submerged and each being greater in size than the Openings in said screen so that in operation they will be held submerged by said screen and vibrate with respect to the under surface of said screen.

'7. The method of rendering a liquid submerged vibratory foraminous screen nonblinding, which comprises: imprisoning below the screen a plurality of loosely disposed cleaner bodies each have in a density less than the liquid medium in which they are submerged and each being greater in size than the openings of said screen, said bodies normally being held against the under surface of said screen bythe buoyancy effect of said liquid medium; and moving said screen repeatedly within and relative to said liquid in a manner to cause movement of said cleaner bodies relative to said under surface, of said screen.

8. A method of cleaning a foraminous screen to free, it from blinding bodies which comprises; submerging said screen in a body of liquid; ime prisoning below said screen a plurality of loosely disposed cleaner bodies held against the under surface of said screen by the buoyancy effect of the liquid, said bodies being of greater size than the openings in said screen; and repeatedly moving said screen in said liquid in a manner to cause movement of said cleaner bodies relative to the under surface of said screen.

SCHNEIDER- References Cited in the file of this pa ent UNITED STATES PATENTS Number 

